Although it's controversial, Jared Diamond's "Guns Germs, and Steel" illustrates several of the key issues facing Mesoamerica that would have to be overcome for it to match Europe technologically and colonize it in any meaningful way post 1 AD. IMO, your best bet would be for someone in the Northeast USA to develop sailing technology to accidentally cross the Atlantic and colonize a small portion of Ireland or or Scotland sometime before 900AD or so. Kind of a reverse of the Vikings.